1. Field of the Invention
The present invention relates to a portable data transmitting/receiving apparatus for receiving digital data sequentially output from each measuring unit, temporarily accumulating the data in a data memory, and collectively transmitting the accumulated data to an external data processing unit such as a host computer.
2. Description of the Related Art
Various types of product inspection are performed in an inspection process of products in, e.g., a factory. When product inspection for mass production is to be performed, a plurality of types of measuring units are normally arranged along a production inspection line. Objects to be measured (products) flowing on the production inspection line are measured (inspected) by the respective measuring units, and the measurement results are totaled to calculate the quality levels and yield of the products.
According to a known measurement data processing apparatus designed to increase operation efficiency of such product inspection, a circuit for extracting a measurement value as an electrical signal is incorporated in each portable physical or chemical value measuring unit such as a vernier caliper, a dial gauge, and a micrometer. When an operator of each measuring unit depresses a transmission button attached to the measuring unit, measurement data is transmitted to a data input unit through a cable. The data input unit accumulates measurement data sequentially transmitted from each measuring unit in a data memory in a storage section. When the remaining storage capacity of the storage section decreases below a limit value, all the measurement data stored in the data input unit is supplied to a data processing unit such as a host computer installed in a management room or the like through an I/0 unit. The data processing unit calculates the quality levels or yield of the products by using the collectively input measurement data, and displays the calculation result on a CRT display section or prints it out through a printer.
In such a measuring system, however, the respective measuring units and the data input unit are connected to each other through cables. If a cable for extracting measurement data is attached to each measuring unit, it interferes with the operation of the measuring unit operator, and measurement operation efficiency is decreased.
In order to eliminate such a drawback, a portable measuring unit incorporating a circuit for extracting a measurement value as an electrical signal and a very small transmitter for outputting measurement data extracted by the circuit as a radio wave has been developed, as disclosed in U.S. patent application Ser. No. 348,170, filed on May 2, 1989 and now U.S. Pat. No. 4,973,957 issued on Nov. 27, 1990 which is a continuation-in-part of application Ser. No. 111,671 filed by Shimizu et al. including an inventor, Okuyama, of the present invention on Oct. 23, 1987, now abandoned, (West Germany Patent Application No. P3736901.6 filed by the present applicant on Oct. 30, 1987). According to this measurement data processing apparatus, an antenna and a receiver are incorporated in a data input unit, so that when a transmission button of each measuring unit is depressed, measurement data is transmitted to the data input unit as a radio wave.
In such an apparatus, however, in order to allow an operator of each measuring unit to confirm that measurement data is reliably transmitted to the data input unit, a small receiver called an answer back unit for receiving a normal response (ACK) signal must be arranged near the operator independently of the measuring unit in addition to a transmitter incorporated in the data input unit. When the operator depresses a transmission button of a given measuring unit, measurement data is, e.g., FSK-modulated and output as a radio wave, and is received by the data input unit. Upon normal reception of the measurement data, the data input unit outputs the ACK signal as a radio wave to the answer back unit through the transmitter. Upon reception of the ACK signal, the receiver signals it to the operator by, e.g., turning on a display lamp for a predetermined period of time.
In addition, the data input unit sequentially stores measurement data sequentially supplied from the respective measuring units in an external storage unit such as a floppy disk drive unit (FDD), and prints it out through a printer as needed. The measurement data stored in the external storage unit is collectively supplied to a data processing unit such as a host computer installed in a different room.
The distance between the installation place of the data input unit and the application place of each measuring unit and answer back unit is determined by the output value of a transmitter incorporated in the measuring unit. It is found that the maximum distance is about 10 m.
A data input unit must be arranged in such a measuring system for the following reasons. Each measuring unit is used in a place near a manufacturing site. In consideration of high-frequency noise and the like, it is not proper to install a data processing unit such as a host computer in such an environment. If a large amount of measurement data upon successive measurement is to be stored in each measuring unit itself, an additional electronic device such as a storage device must be incorporated in the measuring unit. As a result, each measuring unit is increased in size, and its operability decreases. For these reasons, measurement data obtained by each measuring unit is temporarily accumulated in a data input unit arranged near a measurement site, and is supplied to a data processing unit installed in a management room through leads or a storage media of an external storage unit.
As described above, it is difficult to incorporate a receiver (answer back unit) for receiving the ACK signal in a measuring unit, because the size of the measuring unit itself is undesirably increased. In addition, the following problem is left unsolved. If a receiver for receiving the ACK signal is incorporated in each measuring unit, the manufacturing cost of the overall measuring system is increased. Furthermore, an operator cannot directly confirm, by only the form that the normal response is represented by the illumination of a display lamp or buzzer sound representing "correct" or "incorrect", that the transmitted measurement data is correct measurement data obtained by actual measurement.
In addition, in a manufacturing site in a factory, an operator may be required to carry a measuring unit about in the manufacturing site and measure a physical value in each manufacturing step of a product, instead of performing measurement at a predetermined position of a product inspection line or the like. In such a case, the distance from the measuring unit and the answer back unit to a data input unit often exceeds a distance limit of 10 m. In this case, therefore, measurement data cannot be collected in the data input unit by radio transmission.
In some cases, measurement is performed by using a simple measuring unit without a circuit for converting a measurement value into an electrical signal. In such a case, an analog measurement value obtained with the naked eye is temporarily recorded on a notebook or the like. Thereafter, the recorded measurement value must be directly input in a data processing unit through a keyboard.